I just finished reading Eugene Rogan's book The Fall of the Ottomans.
The vast majority of the book covers the years 1914 - 1918 (i.e. WWI), before concluding with the redistribution of the Ottoman Empire by the victors from 1918 to 1920.
Rogan discusses how the redistribution of the land at this time is the ultimate cause of the major aspects of conflict that occupy much of the Middle East up to the present day. Some examples:
How did the dynamic of peace actually change in these regions following WWI?
Was there much more peace prior to the Great War?
If someone were to argue that the European powers are responsible for the conflict in the Middle East up to the present day, would there be a good response through arguing that conflict was rife even prior to the War?
I suppose it depends on what you mean by "peace". If you mean armies engaging in stand-up fights, there hadn't been one of those since the end of the Egypt-Ottoman war in the early 1830's. There had been rather a lot before that though, and 80 years without a major war* in many places would not be all that impressive. But perhaps in the Levant it is.
If you mean that the common people had the ability to live their lives free from fear of random uprisings of violence, not really.
In this period, the Sublime Porte's firmans (decrees) of 1839 and, more decisively, of 1856 — equalizing the status of Muslim and non-Muslim subjects — produced a
"dramatic alienation of Muslims from Christians. The former resented the implied loss of superiority and recurrently assaulted and massacred Christian communities — in Aleppo in 1850, in Nablus in 1856, and in Damascus and Lebanon in 1860. Among the long-term consequences of these bitter internecine conflicts were the emergence of a Christian-dominated Lebanon in the 1920s - 40s and the deep fissure between Christian and Muslim Palestinian Arabs as they confronted the Zionist influx after World War I. "
I think its fair to say that Benny Morris (the author of that inner quote above), would argue that any history of the ethnic conflict in the region that doesn't go back before WWI is missing some important details.
The 1860 massacre Morris mentioned was by some accounts a full-blown Civil War, in which around 23,000 people died (many if not most civilians).
Afterward there was a rising tide of Arab Nationalism. The Ottoman approach from that point appears to have been to break the area up into smaller and smaller administrative units. That may have helped keep a bit of a lid on things for a few more decades, but when WWI broke out the Ottomans tried to suppress the nationalists, which touched off a full-blown rebellion.
This is not the picture of a contented, happy area.
* - If we count the Lebanese Civil War, it was only 50 years.